In many situations in which a liquid comes in contact with a medical administration set such as a filter housing, gas-filled bubbles which cling to the surfaces of the housing may be formed as a result of gas dissolved in the liquid or which may be introduced into the liquid during the course of carrying out a particular procedure, e.g. the oxygenation of blood. In many instances, the presence of such bubbles has little effect on either the filtration process, flow properties, or downstream occurrences. However, in situations where it is desirable to maintain a constant flow rate, variations in flow caused by the generation of gas bubbles is undesirable. In other situations, the introduction of bubbles may adversely affect processes downstream of the filter housing. specifically, in medical applications when a patient is infused intravenously with parenteral fluids, the introduction of bubbles can prove life-threatening to the patient.
Various complications can arise from air bubbles in such medical apparatus. In the apparatus itself, air can block or reduce the effective surface area of a filter, thereby decreasing the efficiency of the apparatus as a whole. Also in the process of using such apparatus, there exists the inherent danger of bubbles being introduced into the patient and forming an air embolism.
Introducing air into the circulatory system of a patient can lead to serious consequences. Small amounts of air can be swept with the blood through the heart without adverse effects. However, bubbles may lodge in the small blood vessels. This can markedly increase the resistance to blood flow, and flow can be reduced or even eliminated. Blockage of small vessels in the brain may lead to serious or even fatal neurological abnormalities. Blockage of the coronary arteries can cause myocardial damage.
In addition, air which enters the venous blood may eventually clog the vessels of the lungs, resulting in diffuse pulmonary embolism. The air has a large surface tension at the interface between the blood and air so that globules of air cannot be deformed enough to be pushed along the capillaries. The physical effects of diffuse pulmonary embolism on the pulmonary circulatory system are similar to those of massive pulmonary embolism, i.e., increased pulmonary circulatory resistance with resulting increase in pulmonary arterial pressure and failure of the right side of the heart. However, with diffuse embolism, the pulmonary vessels appear to develop considerable vasospasm which adds additional resistance to flow besides that caused by the emboli themselves. Patients with this type of embolism exhibit a rapid respiratory rate because of local irritation by the emboli in the lungs and also because of resultant ischemia throughout the body.
It is therefore desirable to eliminate gas bubbles from the administration set in an expeditious manner. This is of particular concern when transparent components are used in the administration set. In such instances, users are tempted to removed entrained gas bubbles by striking the equipment with a reflex hammer. This is dangerous from the standpoint of potential leakage by virtue of a broken part, and also because of the potential to cause misfunction of the component.
Additionally, time is often of the essence for procedures in which administration of parenteral fluids is involved. Expeditious removal of adhered gas bubbles allows the timely used of said equipment in, for example, life threatening situations.
The subject invention is directed then to a method for treating medical administration sets with which parenteral liquids come in contact to reduce the adhesion of bubbles to the equipment and allowing expeditious removal by venting of these bubbles, thereby reducing the danger of introducing undesirable components into a patient and the corresponding likelihood of embolism formation.